The invention relates to an IC package mold lock and methods for making the same. More particularly, the invention relates to leadframe-to-plastic lock structures and methods for use in IC packages.
It is well known to encapsulate IC devices in packages in order to protect the device and to provide connective leads for coupling the terminals of the IC to the outside world, such as a PC board.
Problems are encountered with packaged IC devices used in the arts both in the manufacturing stages and in testing and use. Among the problems, some of the most common and debilitating are the separation of layers of devices, lead fingers pulling out of the package, and open or short circuits caused by separation of materials or the ingress of moisture between separated materials. Attempts to improve the bond between leadframes and package materials have been made using stamped or etched vias in the leadframes, which are then filled with encapsulant. Although somewhat resistant to sheering, these efforts have enjoyed limited success.
Improved leadframe-to-plastic IC package locks would be useful and advantageous in the arts. Such leadframe locks would provide increased reistance to sheering and separating forces providing a more secure bond.
In carrying out the principles of the present invention, in accordance with an embodiment thereof, a method of making an IC package mold lock includes steps of providing a first niche in a leadframe surface and providing an opposing niche in an opposing leadframe surface. The first niche and opposing niche partially intersect, defining an aperture in the leadframe. The niches are arranged such that a key is defined by the intersecting and nonintersecting portions of the niches. The key is encapsulated with mold compound to form a mold lock.
According to one aspect of the invention, an IC package mold lock device includes a leadframe having at least one aperture. The aperture has a key with mold compound disposed in the aperture and encapsulating the key forming a mold lock.
According to another aspect of the invention, an IC package mold lock is provided with a key having a first niche in a surface of the leadframe axially unaligned with a partially intersecting opposing niche in an opposing surface of the leadframe. The niches are of approximately identical same size and shape, the key structure resulting from their nonalignment.
According to yet another aspect of the invention, an IC package mold lock is provided with a key including a first niche in a surface of the leadframe axially aligned with a partially intersecting opposing niche in an opposing surface of the leadframe. The niches are aligned, but not identically shaped, the key structure resulting from their shape difference.
According to still another aspect of the invention, an IC package has a leadframe having a die pad and multiple of lead fingers. A number of apertures in the leadframe are provided, at least one of which has a key. Mold compound encapsulates the key to form a mold lock.
The invention provides technical advantages including but not limited to providing an IC package mold lock ensuring a secure mechanical bond between the leadframe and encapsulant of an IC package. The invention may be used advantageously to provide improved bonds for lead fingers or die pads in DIP, QFN, SOP, or other semiconductor device packages. These and other features, advantages, and benefits of the present invention will become apparent to one of ordinary skill in the art upon careful consideration of the detailed description of representative embodiments of the invention in connection with the accompanying drawings.